1. Field of the Invention
The present invention relates to a process for the production of olefinically unsaturated isocyanates from isophorone diisocyanate and selected olefinically unsaturated carboxylic acids, to the resulting olefinically unsaturated isocyanates and to their use as binders in one-component coating compositions which may be cured at room temperature.
2. Description of the Prior Art
Coating compositions based on isocyanate functional prepolymers containing urethane groups which are processed as one-component products have long been known (Houben-Weyl, Methoden der organischen Chemie, Volume E20, page 1646, Georg Thieme Verlag 1987). They are produced by the reaction of diisocyanates or modified diisocyanates with higher functional polyols such as polyether or polyester polyols. The relatively high molecular weight structure imparts to these compositions good film-forming properties and good optical properties in the resulting coating. However, the high molecular weight structure also causes a higher viscosity so that the coating compositions can only be used as binders when highly diluted or in combination with a considerable proportion of monomeric diisocyanate. Such high concentrations of monomeric isocyanate are physiologically unacceptable and the use of large quantities of solvents cannot be justified from an environmental point of view.
Based on commercially available materials one must choose between high molecular weight, highly functional products with a high viscosity but advantageous properties or a low molecular weight, low viscosity products with insufficient solvent resistance and insufficient drying properties. A need exists for low viscosity products which possess the properties of high viscosity products.
One-component systems which can be cross-linked oxidatively have been described in addition to isocyanate functional coating materials (Ullmann, Encyclopadie der technischen Chemie, 4th Edition, Volume 19, pages 75 et seq, Verlag Chemie Weinheim, Deerfield Beach Fla., Basle, 1980). These one-component systems also can only be used in dilute solutions as binders for coating materials.
It is an object of the present invention to provide new low viscosity binders for solvent-free or low solvent coating compositions with good properties and rapid chemical drying at room temperature which may be universally used and are physiologically harmless.
This object may be achieved with the process according to the invention described below which results in products which satisfy the above-mentioned requirements for the simultaneous presence of olefinic double bonds, amide groups and optionally urethane groups and isocyanate groups. One essential feature is the balanced ratio of amide groups, isocyanate groups and double bonds which are capable of oxidative cross-linking.